Armrest for a chair



FIG. 1 is a perspective view from the front, top and left side of an armrest for a chair showing my design;

FIG. 2 is a front view thereof (the rear view being a mirror image thereof);

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom plan view thereof. 

The ornamental design for an armrest for a chair, as shown. 